An exhaust gas purification device is normally used to purify exhaust gas with a catalyst arranged in an exhaust passage of an engine. For instance, the catalyst purges NOx by causing a reaction between NOx and HC in the exhaust gas. However, a sufficient amount of HC is not contained in the exhaust gas of a diesel engine. Accordingly, in patent documents 1 to 3, additive devices supply catalysts with diesel oil, which serves as fuel, as an additive to compensate for the lack of HC.
In the structures disclosed in patent documents 1, 2, an additive nozzle for supplying additive is attached to a branched pipe of an exhaust manifold. In this structure, the additive injected from the additive nozzle is blown back by the pressure of the exhaust gas discharged from the cylinders. This results in a shortcoming in which the blown-back additive clogs the additive nozzle.
[Patent Document 1] Japanese Laid-Open Patent Publication No. 2001-280125
[Patent document 2] Japanese Laid-Open Patent Publication No. 2003-201836
[Patent document 3] Japanese Laid-Open Patent Publication No. 2006-22787